The invention generally relates to oscillating piston engines. More specifically, the present invention relates to an oscillating piston engine of the type having a housing in which a first and at least a second piston are arranged which can jointly revolve in the housing about an axis of rotation which is fixed in relation to the housing, and which perform when revolving about the axis of rotation reciprocating pivoting movements in opposite directions relative to one another about a pivot axis running through the center of the housing perpendicularly to the axis of rotation, wherein a working chamber is arranged between mutually facing end surfaces of the first and at least second piston, and which further comprise at least one gas exchange opening in the housing for admitting or discharging a gas into or from the working chamber.
Oscillating piston engines and in particular an oscillating piston engine according to the present invention can be used as internal combustion engines, as pumps or as compressors. An oscillating piston engine according to the present invention is preferably used as an internal combustion engine and is described as such in the present description.
In the case of the use of an oscillating piston engine as an internal combustion engine, the individual working strokes of admitting, compressing, expanding and expelling are imparted by reciprocating pivoting movements of the individual pistons between two end positions.
In the case of the oscillating piston engine known from document WO 03/0670333 A1 from the same Applicant, four pistons are arranged in the spherical housing which jointly revolve about an axis of rotation which is central to the housing and fixed in relation to the housing and perform when revolving in the housing reciprocating pivoting movements about a pivot axis, each two adjacent pistons pivoting in opposite directions. In the case of this known oscillating piston engine, each two pistons diametrically opposing the center of the housing are rigidly connected to each other to form a double piston, and two such pairs of pistons are arranged crosswise in the center of the housing. A respective working chamber is formed between each two mutually facing end surfaces of the pistons of the pairs of pistons, so that the known oscillating piston engine has a total of two working chambers. Both working chambers, which are arranged diametrically opposing the center of the housing, increase and decrease in size in the same direction during the reciprocating pivoting movement of the pistons.
The pistons of this known oscillating piston engine are arranged in the housing in such a way that they are located in their TDC position, in which the volumes of the two working chambers are minimal, perpendicularly to the axis of rotation. In this position, as the pistons revolve about the axis of rotation, the centrifugal forces acting on the pistons are maximal. As a result, at high rotational speeds, the expanding or the pivoting-apart of the pistons must take place counter to the centrifugal forces, because the centrifugal forces counteract the pivoting-apart movement of the pistons. In the case of this oscillating piston engine, the working chambers are located in all cases outside and perpendicularly to the axis of rotation.
Furthermore, the known oscillating piston engine has in the housing two gas exchange openings, which are arranged at an angular distance of approximately 100° from one another relative to the axis of rotation. One gas exchange opening serves to admit combustion air and the other gas exchange opening serves to expel the combusted fuel/air mixture. A spark plug is arranged on the side of the axis of rotation opposing the gas exchange openings, for example on the bisector of an angle between the two gas exchange openings.
An oscillating piston engine which is comparable to the above-described known oscillating piston engine is known from document WO 2005/098202 A1. As in the case of the above-described known oscillating piston engine, admission pressure chambers are associated with the backs of the pistons that are remote from the working chambers. For flooding the admission pressure chambers with atmospheric fresh gas, intake openings are provided in the housing, and for flooding the working chambers with precompressed fresh gas, the admission pressure chambers are connected to the working chambers via a connection opening and via an overflow channel. The output shaft located on the axis of rotation is provided on its end face with rotary slide valves which each have two opposing windows which can be drawn together with the intake openings and with the connection opening, wherein on rotation of the shaft through 180° alternately all four windows clear the intake openings and two of the windows clear the connection openings of the overflow channels. The actual gas exchange openings, which are associated with the working chambers, are provided with controlled valves, and this increases the design costs. This known approach of providing a control disc rotating about the axis of rotation or a rotary slide valve is known, in the case of a comparable oscillating piston engine, also from document U.S. Pat. No. 6,325,038 B1.